What this 4-pole MCB does on the rail
The Siemens 5SL4403-7 is a 4-pole (4P) miniature circuit breaker from the SENTRON family, rated 3 A at 400 V AC with a C-curve tripping characteristic.
Mounting and integration — DIN-rail fit
Mounting position is any orientation, so vertical or horizontal rail layouts work.
Rated 3 A at 30 °C ambient, but the current must be derated as panel temperature rises: 2.88 A at 40 °C, 2.82 A at 45 °C, and 2.69 A at 55 °C. The breaker itself is rated for ambient up to 75 °C (storage -40 °C), with 95% humidity max at 55 °C.